Electric cable.



J. L. CONRAD. ELECTRIC CABLE. APPucATloN FILED Dic. 8, 1914.

Patented Qot. 19,1915.

Witnesses Attbrneys narran JOSEPH L. DNRAD, CLE DURHAM. NORTH CAROLNA,ASSIGNOR OF @NE-THIRD TO THOMAS I). WRGfI-IT AND ONE-THRD TO ARVID S.HALSTROM, OF DURHAM, NORTH CAROLINL..

memos.,

Application led December 8, 1914.

To all 'whom it may concern.'

Be it knownthat l, JOSEPH L. CONRAD, a citizen of the United States,Yresiding at Durham, in the county of Durham and State of North Carolina,have invented new and useful Electricv Cable, of which the following isa speciiication.

The present invention appertains to electric cables, and aims to provideanelectric cable provided with novel means to facilitate the locationand clearing of faults or defects in the cable, in order that the faultsor defects ductor or conductors.

It is also within the scope of the invention, to provide a cableprovided with detecting means of the nature indicated, which will becomparatively simple and inexpensive to manufacture, and which will beeiiicient and practical in use.

With the foregoing and other objects in view which will appear as thedescription proceeds, the invention resides in the combination andarrangement of parts and in the -details of construction hereinafterdescribed and claimed, it being understood that changes in the preciseembodiment of the invention herein disclosed, can be made within thescope of what is claimed, without departing from the spirit of theinvention.

The invention is illustrated in the accompanying drawing, Wherein1-Figure 1 is a fragmental perspective of an electric cable embodying the'present im'- provements. F ig.' 2 is across sectional view thereof. Fig.3 is a cross sectional view of another cable embodying a modification.Fig. 4 is a view similar to Fig. 1, illustrating a variation.

In the drawing, there isillustrated a multifj p wire core embodying ,aplurality of conductors or Wires 1, each of which is wrapped I orcovered by suitable insulation 2, although it is to be understood thatthe core may coml Specication of Letters Patent.

ELECTRIC CABLE.

lllatented @et 19, 1915.

Serial No. 876,152.

prise a single conductor or wire with the same result. i

ln carrying out the invention, the conductors or core wires 1, havingthe insulation 2, are embraced by a wrapping, braiding or layer ofinsulation 3 of any suitable material, and which may be saturated with asuitable moisture-proof material or compound, to render the insulation 3moistureprooi, for protecting the core or conductors.

Surrounding the insulation 3, are a plurality main conductors 1 and theauxiliary or detector conductors 4.

Thereis illustrated in Fi'g.l1, a conductor 7 connected at one terminalto the conductor 4, and at the other terminal to the sheath 6, so as tobe in circuit with the conductor 4 and sheath 6, the conductor 7 beingprovided with a battery or other suitable source of electric current 8,and having interposed therein,.a galvanometer or current detector 9.Thus, should the seal of the cable be broken, and the moisture attractedby the insulation 5y of the detector conductor 4, a circuit would be setup through the conductor 7, sheath 6, and conductor 4, and thegalvanometer 'or indicator 9 would Warn the attendant or observer of thedefect-or fault in the cable, and through the medium of the detectorconductors 4, the fault or defect could be traced by using theconductors 4 as pilots, in connection with suitable apparatus for thepurpose, it being observed that the nearer the galvanometer conductor 7is located to the defect, the greater will be the deflection of thegalvanometer' needle.` Thus, when a defect or fault occurs, this factwill be signaled by the deflection of the,"`

or farther away from the defect. The greatest amount of deflection ofthe galvanometer needle will occur adjacent the defect, so that it iscomparatively easy for the defect or fault to be located. It theresistance of the conductors 4 and sheath 6 is known, as well as thevoltage of the battery 8, the approximate distance between the detectand4 conductor 7 may be determined by noting the amount of deflection ofthe galvanometer needle or pointer, as will be apparent to those versedin the art, since the farther away the defect is from the conductor 7,the greater will be the resistance offered by the sheath-6 andrespective conductor 4, and the less will be the deflection of thegalvanometer needle. It is assumed that in the case above mentioned, thesheath or casing 6 is of lead or other material which is a conductor ofelectrical energy.

In case that the sheath or casing 6 is a non-conductor, the detectorconductors 4 which are disposed between the insulation 3 an'd sheath 6,are arranged' in pairs, being preferably intertwisted, and they arenormally insulated from each other by the absorbent moisture attractinginsulations 5 thereon. Vith -the use of the pair of detector conductors4, the terminals of the conductor 7 having the battery or source ofcurrent 8 and the galvanomete'r or detector. 9 interposed therein, areconnected to the conductors 4 of the respective pair, and.i

should moisture be present Within the sheath 6, the same would beattracted by the insula- 'tions 5 of the pair of conductors .4, whichwould close the circuit through the conductors 4 and 7 so that thegalvanometer 9 would -indicate the fact that a fault or defeet hasoccurred inthe cable.

The insulation 3 is of advantage, since it provides a secondmoisture-proof seal around the core or main conductor or conductors, sothat aleakage or seepage-of moisture through the sheath 6, will notimmediately result in the penetration of the moisture to the core, sincethe insulation 3 would excludelthe moisture from` the core, for asufficient length of time, until the fault or defect could be locatedand repaired. The use of the absorbent moisture attracting insulations 5for the detector conductors 4 -is of prime importance, since it enablesthe detecting current to be set up immediately after the seal of thecable is broken and moisture is admitted into thesheath, and it istherefore possible for the break to be located with comparative ease, sothat the fault or defect can be repaired Without damage to the core orconductors and a resultant imor other cables with equal propriety andsucabove described, and the detecting circuit pairment or interferencewith the electrical service ot' whatever character it is, it being notedthat the present invention may be employed upon telephone, telegraph,lighting cess. The utility of the invention is enhanced materially it'the insulation 5 of each detectorconductor 4 is saturated or impregnatedwith the salts of potassium or other chemical solution,compound orsubstance for attracting moisture, which will liquefy when exposed toair, to quicken the closing of the detector circuit.

The detector conductors in the forms illustrated in Figs. l. 2 and 4preferably lie dormant or inactive under normal conditions, whereas inthe form illustrated in Fig. 3, a portion of the live or activeconductors are utilized as detector conductors. Thus, Fig. 3 illustratesan vordinary cable embodying the insulated core or conducting wiresinclosed by a lead or other sheath or casing 6. The core wires orconductors are divided into a central group 1 and a surrounding layer orgroup l". A mois- 90 ture-proof insulation 3 is twisted or otherwiseprovided around the central conductors l', to exclude moisture from theselected central conductors, whereas the outer con ductors l aredisposed outside of the insulation 3 to be first exposed to any moisturepresentwithin the sheath G. The insulation'Q of the central conductors lmay be of any suitable character, and need not especially bemoisture-proof, since the central conductors are protected sufficientlyby the insulation 3, but the insulation 2 of the outer conductors l isof cotton, silk, paper or other suitable absorbent material, andispreferably saturated or impregnated with the moisture attractingchemical or substance above refeired to. Thus, the outer conductors lwill serve as detector conductors, vthe same as the detector conductorsmay be set up through one or more of the conductors l in the samemanner, and Without interfering with the normal use of the conductors l.

The manner of establishing the detecting circuit through the detectorconductor or conductors is only illustrated in its' simplest form in thedrawing, and in practice may be more elaborate and expensive, but `sincethe present invention relates to the cable 72er se and not the detectingapparatus, the latter need not be described or illustrated as used inactual practice. Y'

lVhat is claimed s:-

1. An electric cable comprising a moisture-proof sheath, an insulatedconducting core therein, a detector conductor within the sheath', and anabsorbent moisture-attracts ing insulation for the detector conductor toenable a detecting circuit to be established 110 through the detectorconductor in the presence of moisture Within the sheath.

2. An electric cable comprising a moisture-proof sheath, aconductor coretherein,

a moisture-proof insulation surrounding the core, a detector conductorbetween the said insulation and sheath,y and an absorbentmoisture-attracting insulation for the detector conductor to enable adetecting circuit to be established through the detector conductor inthe presence of moisture within the sheath.

3. An electric cable comprising a moisture-proof sheath, an insulatedconductor core therein, a detector conductor within the sheath, and aninsulation for' the detector conductor impregnated by a moisture-at`tracting substance, to enable a detecting cur- -rent to vbe establishedthrough the de- JOSEPH L. CONRAD. Witnesses:

C. C. MYERS, A. L. 'KIRKLANll

